= form_for @customer do |f|
  - if @customer.errors.any?
    #error_explanation
      %h2= "#{pluralize(@customer.errors.count, "error")} prohibited this customer from being saved:"
      %ul
        - @customer.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :firstname
    = f.text_field :firstname
  .field
    = f.label :lastname
    = f.text_field :lastname
  .field
    = f.label :phonenumber
    = f.text_field :phonenumber
  .actions
    = f.submit 'Save'
